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Search: id:A157562
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| A157562 |
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Half the number of length n integer sequences with sum zero and sum of squares 1800. |
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+0
1
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| 1, 3, 126, 6510, 336015, 19347993, 928126199, 34039360092, 1173329179500, 39563049010881, 1301454506052525, 41455087636231074, 1268529094022948940, 37131123353064641460, 1040240395936575811890, 28055696919876575091824
(list; graph; listen)
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OFFSET
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2,2
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LINKS
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Ron Hardin, Table of n, a(n) for n=2..50
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FORMULA
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[cache enabling] count(n,s,ss)->count(n,t,tt) where t=s mod n, q=(t-s)/n, tt=ss+2*q*s+n*q^2; count(n,t,tt)=sum[i^2<=tt]{ count(n-1,t-i,tt-i^2) }. a(n)=count(n,0,1800)/2.
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CROSSREFS
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Sequence in context: A114877 A152859 A157547 this_sequence A157592 A159319 A086154
Adjacent sequences: A157559 A157560 A157561 this_sequence A157563 A157564 A157565
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KEYWORD
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nonn
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AUTHOR
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Ron Hardin (rhhardin(AT)att.net) Mar 02 2009
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